1 /*

     2  * Copyright (c) 2019, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.

     8  *

     9  * This code is distributed in the hope that it will be useful, but WITHOUT

    10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    12  * version 2 for more details (a copy is included in the LICENSE file that

    13  * accompanied this code).

    14  *

    15  * You should have received a copy of the GNU General Public License version

    16  * 2 along with this work; if not, write to the Free Software Foundation,

    17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    18  *

    19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    20  * or visit www.oracle.com if you need additional information or have any

    21  * questions.

    22  *

    23  */

    24 

    25 #ifndef SHARE_GC_G1_G1COLLECTIONSETCANDIDATES_HPP

    26 #define SHARE_GC_G1_G1COLLECTIONSETCANDIDATES_HPP

    27 

    28 #include "gc/g1/g1CollectionSetCandidates.hpp"

    29 #include "gc/shared/workgroup.hpp"

    30 #include "memory/allocation.hpp"

    31 #include "runtime/globals.hpp"

    32 

    33 class HeapRegion;

    34 class HeapRegionClosure;

    35 

    36 // Set of collection set candidates, i.e. all old gen regions we consider worth

    37 // collecting in the remainder of the current mixed phase. Regions are sorted by decreasing

    38 // gc efficiency.

    39 // Maintains a cursor into the list that specifies the next collection set candidate

    40 // to put into the current collection set.

    41 class G1CollectionSetCandidates : public CHeapObj<mtGC> {

    42   HeapRegion** _regions;

    43   uint _num_regions; // Total number of regions in the collection set candidate set.

    44 

    45   // The sum of bytes that can be reclaimed in the remaining set of collection

    46   // set candidates.

    47   size_t _remaining_reclaimable_bytes;

    48   // The index of the next candidate old region to be considered for

    49   // addition to the current collection set.

    50   uint _front_idx;

    51 

    52 public:

    53   G1CollectionSetCandidates(HeapRegion** regions, uint num_regions, size_t remaining_reclaimable_bytes) :

    54     _regions(regions),

    55     _num_regions(num_regions),

    56     _remaining_reclaimable_bytes(remaining_reclaimable_bytes),

    57     _front_idx(0) { }

    58 

    59   ~G1CollectionSetCandidates() {

    60     FREE_C_HEAP_ARRAY(HeapRegion*, _regions);

    61   }

    62 

    63   // Returns the total number of collection set candidate old regions added.

    64   uint num_regions() { return _num_regions; }

    65 

    66   // Return the candidate region at the cursor position to be considered for collection without

    67   // removing it.

    68   HeapRegion* peek_front() {

    69     HeapRegion* res = NULL;

    70     if (_front_idx < _num_regions) {

    71       res = _regions[_front_idx];

    72       assert(res != NULL, "Unexpected NULL HeapRegion at index %u", _front_idx);

    73     }

    74     return res;

    75   }

    76 

    77   // Remove the given region from the candidates set and move the cursor to the next one.

    78   HeapRegion* pop_front();

    79 

    80   // Add the given HeapRegion to the front of the collection set candidate set again.

    81   void push_front(HeapRegion* hr);

    82 

    83   // Iterate over all remaining collection set candidate regions.

    84   void iterate(HeapRegionClosure* cl);

    85 

    86   // Return the number of candidate regions remaining.

    87   uint num_remaining() { return _num_regions - _front_idx; }

    88 

    89   bool is_empty() { return num_remaining() == 0; }

    90 

    91   // Return the amount of reclaimable bytes that may be collected by the remaining

    92   // candidate regions.

    93   size_t remaining_reclaimable_bytes() { return _remaining_reclaimable_bytes; }

    94 

    95   void verify() const PRODUCT_RETURN;

    96 };

    97 

    98 #endif /* SHARE_GC_G1_G1COLLECTIONSETCANDIDATES_HPP */

    99